When using my L2TP VPN with the Unifi I realised that it was assigning a different IP Address to my client when it connected sometimes.
This wouldn’t normally be a problem if the remote client was only taking to my internal network, however I run a server that my internal network communicates out to via IP Address, so if this changes it all stops working.
This article walks through how to setup a static IP Address for an L2TP Client.